Research on Sintering Dynamics and Microwave Dielectric Properties of Bi and Mn Doped Lead-Based Ceramics

Abstract:

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The sintering dynamics, microstructures and microwave dielectric properties of Bi2O3 and
MnO2 co-doped [(Pb,Ca) La](Fe,Nb)O3 (PCLFN) ceramics were investigated. Bi2O3 and MnO2
dopants effectively enhanced bulk densities and reduced sintering temperatures by about 100~140°C.
Sintering procedure had significant effect on grain size and porosities of ceramics. Investigation of
microstructures revealed that the grain growth was controlled by either volume diffusion or
second-order interface mechanism in present ceramics. The potential microwave dielectric properties
of εr=91.1,Qf=4870GHz and τf=18.5ppm/°C could be obtained when the mass ratio of Bi2O3/MnO2
(k) was 1, the doping content w=1wt% and sintered at 1050°C for 4h.

Abstract: Dielectric characteristics of strontium titanate based ceramics doped with samarium were
investigated within temperature range from –60oC to 150oC. XRD was used to identify the phase
compositions of the ceramics and the microstructures were characterized by SEM. Good temperature
coefficient of capacitance (TCC) was observed: TCC = +18% ~ −11% with high dielectric constant of
18000 and relative low dielectric loss. After further modification, the present ceramics might be
promising candidates for the multilayer ceramic capacitors applications at high temperature.

Abstract: XRD, SEM, bulk density and dielectric properties measurements were used to investigate the
effect of TiO2 nanopowder substitution for conventional TiO2 micro-powder on the sintering and electric
properties of PZT ceramics. Results revealed that the sintering temperature of dense Pb(Zr0.53Ti0.47)O3
ceramics was lowered about 50°C ~ 100°C when 20% and 40% of conventional TiO2 micro-powder was
substituted by TiO2 nanopowder. The electric properties were kept or even enhanced in the PZT ceramics
adopted the TiO2 nanopowder.

Abstract: In this paper, the effect of Nb2O5 on the microstructure and dielectric properties of BaTiO3-based ceramics has been investigated. In the study，Nb2O5 is added to the BaTiO3-based ferroelectric material by conventional solid state synthesis. The structure is identified by X-ray diffraction method and SEM is also employed to observe the surface morphologies of the sample. The specimens of the ferroelectric doped with 2wt% Nb2O5 sintered at 1260°C for 1h exhibit attractive properties, its dielectric temperature coefﬁcient is lower than 15% over a wide temperature range from －55 to +180°C.

Abstract: Microstructures and microwave dielectric properties of Ca(Sm0.5Nb0.5)O3 ceramics, prepared by a conventional solid-state reaction method, were systematically investigated by varying calcining temperature, sintering temperature and cooling rate. The XRD result showed that a single Ca(Sm0.5Nb0.5)O3 phase could be synthesized at a calcining temperature of 1200 °C. Optimized combination of microwave dielectric properties of εr = 22.36, Q×f = 18030 GHz and τf = -31.2 ppm/°C was obtained for furnace-cooled Ca(Sm0.5Nb0.5)O3 ceramics sintered at 1550 °C for 4 h. However, some microcracks were found from the microstructures of the furnace-cooled specimens. Further, the Q×f value could be increased by controlling the cooling rate during the sintering process due to the disappearance of microcracks in the final material. With a cooling rate of 2 °C/min, Ca(Sm0.5Nb0.5)O3ceramics exhibited an enhanced Q×f value of 37130 GHz.

Abstract: The 0.95MgTiO3-0.05CaTiO3 (95MCT) powders and ceramics were prepared by a sol-gel method by using Mg(NO3)2•6H2O, Ca(NO3)2•4H2O and Ti(C4H9O)4 as the starting materials. The effects of calcination temperature on phase formation, morphology and particle size distribution of the proposed powders were examined, and the microwave dielectric properties of 95MCT ceramics made from different size particles were investigated. The dried gels were calcined at 600 °C, 700 °C, 800 °C and 900 °C, and the derived particle sizes of powders were 10-20 nm, 50-100 nm, 60-120 nm and 120-150 nm, respectively. The proper sizes, which range from 50-150 nm, lowered the sintering temperature of 95MCT ceramics effectively from 1400 °C to 1175 °C due to the high surface energy. Sintered at 1175 °C, the 95MCT ceramic prepared from 50-100 nm size particles had compact structure and exhibited good microwave dielectric properties: εr = 21.33 and Q×f = 36,315 GHz.